Naltrexone

[VikrantS137]

Mice that have been given morphine are very likely to develop blood poisoning because bacteria that normally reside in the intestine typically respond to morphine by migrating into the bloodstream. However, when mice are given both morphine and the new drug naltrexone, blood poisoning is much less frequent, although it does still occur. These results provide support for researchers’ prediction that naltrexone will turn out to be toxic to certain types of bacteria.

Which of the following, if discovered to be true, would most seriously weaken the support for the researchers’ prediction?

A. After being administered to mice, naltrexone does not pass from the bloodstream into the intestine.
B. Naltrexone inhibits morphine from triggering the migration of intestinal bacteria into the bloodstream.
C. Mice that have been given naltrexone but not morphine have no greater risk of developing blood poisoning than do mice that have not been given either substance.
D. The increased risk of blood poisoning is not the only harmful effect on mice of being given morphine.
E. Conditions other than the presence of intestinal bacteria in the bloodstream can cause blood poisoning in mice.

OA: B

Naltrexone inhibits morphine from triggering the migration of intestinal bacteria into the bloodstream. Hence, it is not the toxic nature of the naltrexone that makes blood poisoning much less frequent but it is 'Naltrexone inhibits morphine'. Hence, B is the answer.

(1) Is my reasoning correct regarding B?
(2) Why C is incorrect?

[sahilk47]

Mice that have been given morphine are very likely to develop blood poisoning because bacteria that normally reside in the intestine typically respond to morphine by migrating into the bloodstream. However, when mice are given both morphine and the new drug naltrexone, blood poisoning is much less frequent, although it does still occur. These results provide support for researchers’ prediction that naltrexone will turn out to be toxic to certain types of bacteria.

Which of the following, if discovered to be true, would most seriously weaken the support for the researchers’ prediction?

A. After being administered to mice, naltrexone does not pass from the bloodstream into the intestine.
B. Naltrexone inhibits morphine from triggering the migration of intestinal bacteria into the bloodstream.
C. Mice that have been given naltrexone but not morphine have no greater risk of developing blood poisoning than do mice that have not been given either substance.
D. The increased risk of blood poisoning is not the only harmful effect on mice of being given morphine.
E. Conditions other than the presence of intestinal bacteria in the bloodstream can cause blood poisoning in mice.

OA: B

Naltrexone inhibits morphine from triggering the migration of intestinal bacteria into the bloodstream. Hence, it is not the toxic nature of the naltrexone that makes blood poisoning much less frequent but it is 'Naltrexone inhibits morphine'. Hence, B is the answer.

(1) Is my reasoning correct regarding B?
(2) Why C is incorrect?

Hi

I feel option C is not relevant to the argument. Author's conclusion is that Naltrexone is toxic to certain types of bacteria.
Since the question asks us to weaken this link between Naltrexone and bacteria, we need to determine whether there is something else (apart from Naltrexone) that is reducing the stated migration of bacteria to bloodstream and is correspondingly reducing the likelihood of blood poisoning. Option B does the job by stating that Naltrexone inhibits morphine from triggering the migration of intestinal bacteria into the bloodstream, rather than acting toxic to bacteria.

Option C on the other hand states that Mice that have been given naltrexone but not morphine have no greater risk of developing blood poisoning than do mice that have not been given either substance. To rephrase option C: Level of risk from the intake of only naltrexone and no morphine equals the level of risk from the intake of no naltrexone and no morphine. Thus, independently, intake of naltrexone will not increase risk of blood poisoning. However, option C does not say anything about naltrexone's impact on bacteria or how it is causing/ not causing blood poisoning.

Thank you

[Chelsey Cooley]

Your reasoning for B is totally correct. B represents a very common type of correct "weaken" answer on the GMAT. The conclusion to the argument suggests a reason why something is happening : in this case, it suggests that the reason naltrexone helps prevent blood poisoning is that it's toxic to bacteria. One thing to look for among the answers, when you see this type of argument and are asked to weaken it, is an answer that provides an alternative, more compelling reason for what's happening. In this case, B tells us what the actual reason is: it doesn't kill the bacteria, it just keeps it from moving to the bloodstream.

If we break down C, what is it really saying? Basically, it tells us that naltrexone doesn't cause blood poisoning. (If that doesn't seem clear right away, spend some time thinking about it - why does C seem to prove what I just wrote there?) Now, in order to weaken the argument, we would have to show that naltrexone might not be toxic to bacteria. B did that successfully. But does just demonstrating that naltrexone doesn't cause blood poisoning, show that it isn't toxic to bacteria? No, it doesn't really tell us whether it's toxic to bacteria one way or the other. (It just tells us that it isn't toxic to the poor mice. )